1. Field of the Invention
The present invention relates to a recording and reproducing method and a recording and reproducing apparatus using a dyestuff-based, write-once DVD medium, and to an optical recording medium.
2. Description of the Related Art
Currently, the development of DVD-Rs as next-generation, large-capacity optical disks is advancing. The development of techniques such as the development of recording materials for miniaturizing recording pits, the use of image compression techniques typified by Moving Picture Experts Group-2 (MPEG2), the shortening of wavelengths of semiconductor lasers used for recording pit reading, and the like are needed as essential techniques for improving the recording capacity.
Heretofore, only an AlGaInP laser diode of a 670 nm band for a barcode reader or a measuring device has been merchandized as a semiconductor laser for the red wavelength region. However, as optical disks become more high density, red lasers are earnestly being used in optical storage markets. In the case of DVD drives, they are standardized at a wavelength of a semiconductor laser of the 630 to 690 nm band as a light source. On the other hand, DVD-ROM drives dedicated for reproduction are merchandized at a wavelength of about 650 nm.
Generally, in dyestuff-based, write-once DVD media at which pits (marks) are formed by a heat mode, the recording power and the pulse width of the recording pulse train formed by laser light emission at the time of recording is optimized at a specific recording speed, and the states of marks and spaces which are formed at different recording linear speeds vary. Namely, the jitter characteristic worsens due to insufficiency in the heat capacity arising due to the leading heating pulse needed for mark formation, dispersion in the average lengths of the marks due to different heating temperatures reached with respect to the optimal decomposition temperature, uniform mark widths being unable to be obtained due to the duty ratios of the optimal heating pulses being different, and the occurrence of thickening or thinning in accordance with the mark lengths.
Further, with respect to the physical formats of DVD media, in the case of the format of a DVD-R medium, it is standardized in a format in which a portion of a land portion called a land prepit is cut. When this method is adopted, at a land prepit signal (LPPb) of less than 0.16, prepit information such as the prepit address and the like cannot be reproduced well, and when it exceeds 0.32, the LPP signal itself exhibits noise-like behavior in the data region and many data errors arise. Accordingly, for the LPP, a cut width which suits the recording medium is finely-adjusted at a stamper, and the land cut width must be controlled such that LPPb is in a range of 0.16 to 0.32.
As the optical recording media using a dyestuff in the recording layer, there are, for example, a medium using a polymethine dyestuff or a polymethine dyestuff and a light stabilizer as a recording material (see Japanese Patent Application Laid-Open (JP-A) No. 10-181211), a medium using a tetraazaporphyrin dyestuff as a recording material (see JP-A No. 2002-283721), a medium using a cyanine dyestuff and an azo metal chelate dyestuff (a salt-forming dyestuff) as recording materials (see International Publication No. WO 98/029257), media using an azo metal chelate dyestuff as a recording material (see JP-A No. 2000-127625 and JP-A No. 11-310728), a medium using a formazan metal chelate dyestuff as a recording material (see JP-A No. 2001-023235), a medium using a dipyrromethene metal chelate dyestuff as a recording material (see JP-A No. 10-226172), a medium using a squarylium metal chelate dyestuff as a recording material (see JP-A No. 2002-370451), and the like. Further, many media which use dyestuffs in recording materials and carry out multi-pulse recording also are known (see JP-A No. 2000-182244 and JP-A No. 2000-207742). However, there is no disclosure or suggestion of structures which carry out recording on dyestuff-based, write-once DVD media by one pulse and which focus on the relationship with the recording waveform at the time of carrying out high linear speed recording.
Accordingly, the current situation is that there is desired the development of a recording and reproducing method and a recording and reproducing apparatus which can obtain a good recording waveform and can carry out even higher linear speed recording on dyestuff-based, write-once DVD media.